Various compact arrangements for cooling heat generating components of circuit packs within a supporting cage are known in the prior art.
A typical example of the prior art is U.S. Pat. No. 4,860,163, issued to Alan Sarath on Aug. 22, 1989 and entitled "Communication Equipment Cabinet Cooling Arrangement", which is incorporated herein by reference for background informational purposes. A similar arrangement is shown in FIGS. 1 and 2 herein, to illustrate the background prior art.
In FIG. 1A, there is illustrated a cut-away view of a communication equipment cabinet 10 having circuit pack cage 20 inserted therein. As shown circuits packs 21 are mounted in respective circuit pack guides 22 formed in the interior of circuit pack cage 10. Each of the circuit packs 21 are shown having a number of heat generating components 26 affixed thereto.
A plurality of louvers 12 formed in front door 11 of cabinet 10 allow a stream of cooling gas, for example, air, to enter cabinet 10 and flow over and cool the heat generating components 26. The stream of cooling gas exits circuit pack cage 20 via spaces 27 formed between adjacent circuit pack guides 22 and flows into ducts 17 and 18. The stream of cooling gas flowing into ducts 17 and 18 is then directed to plenum 40 where it is exhausted by the forced convection provided by blower fan 19 mounted in proximity to rear door 16.
FIG. 1B illustrates a top cut-away view of the arrangement of FIG. 1A, in which like elements retain the same designations. As can be seen, a stream of cooling gas as represented by the direction of the arrows depicted in FIG. 1B enters cabinet 10 via louvers 12 (not shown in FIG. 1B) formed in front door 11. As shown, the flow of cooling gas is directed over the heat generating components and thence into ducts 17 and 18. Once in ducts 17 and 18, the stream of cooling gas then flows into plenum 40 where it is exhausted by blower fan 19, as discussed previously.
While such compact fan blower schemes of the prior art provide some advantages, there are also some limitations. Continuing development of circuit packs is leading to higher component densities, and to greater amounts of heat generated by ever more sophisticated electronic components, operating at ever higher frequencies. Such continuing developments require an enhanced volume of air flow (or flow of other cooling gas) at enhanced static pressures to provide cooling, while still maintaining a desirable compact arrangement.
Another requirement is to reduce the audible noise levels of cooling systems, which has been objectionable to personnel who operate the circuit packs. In some cases, high levels of audible noise has impaired operator performance. Unfortunately, when blower fan speeds are reduced to the point at which the acoustic noise levels are not objectionable to the operator, or impair operator performance, the cooling provided may be inadequate.
Another requirement is for a substantially uniform flow of air (or other cooling gas) to cool such electronic components. If the flow is not substantially uniform, there may exist inadequate cooling in specific locations within the cage. This means that when the flow is inadequate for the circuit pack, the circuit pack could experience functional deficiencies that include premature failure or produce erroneous performance results. This flow should be substantially uniform from circuit pack to circuit pack, as well as from front to rear of each circuit pack.
Previous solutions include, but are not limited to, multiple tube axial fans. The airflow from these devices must be conditioned to provide uniform distribution within the cage of circuit packs. This is difficult to accomplish due to the turbulent flow exiting these devices.
What is needed is a compact apparatus for cooling circuit packs in a supporting cage, which provides a substantially uniform flow of coolant at enhanced volume and static pressure, while reducing ambient noise level.